Visualization and Organization of Collagen VI Containing Suprastructures in Articular Cartilage.

The extracellular matrix (ECM) is composed of different networks with unique functional and structural characteristics that are formed by specific macromolecular suprastructures composed of proteins, glycoproteins, proteoglycans, and glycosaminoglycans. Collagen VI is a ubiquitous component of the ECM present in virtually all tissues and interacting with a wide range of extracellular matrix molecules, including collagen I, II, IV, perlecan, decorin, biglycan, hyaluronan, heparin, fibronectin, as well as transmembrane receptors like integrins. In cartilage, collagen VI is enriched in the pericellular matrix, a basement membrane-like structure, surrounding each chondrocyte and important for transduction of biomechanical and biochemical signals to the cells. Since the supramolecular aggregates of collagen VI are complex composite structures, a major challenge will be to visualize these structures by electron microscopy.